Method for decomposing iodofluorocarbons

Abstract

To provide a practical decomposition method for decomposing iodofluorocarbons under mild conditions into fluoroacetic acids and / or inorganic fluorides, the method featuring cost-efficiency, safety, and industrial applicability.SOLUTION: A method for decomposing iodofluorocarbons includes reacting one or more iodofluorocarbons with a base in a solvent, where the iodofluorocarbons are represented by general formula (1): Rf-I (1) (where Rf is a C2-20 linear or branched fluoroalkyl group, optionally containing one or more iodine atoms).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for decomposing iodofluorocarbons. Iodofluorocarbons are useful compounds used as chain transfer agents in fluoropolymer synthesis, water and oil repellents, emulsifiers, etc., but in recent years, environmental and toxicological issues have been pointed out, and there is a demand for some kind of decomposition of surplus materials and by-products during production to be rendered harmless. Iodofluorocarbons are decomposed into fluoroacetic acids and / or inorganic fluorides under mild conditions. [Background technology]

[0002] A commonly known method for decomposing iodofluorocarbons is incineration at high temperatures, but this method has the drawback of being costly and energy-intensive. In addition, hydrogen fluoride and hydrogen iodide generated during incineration are expected to accelerate the deterioration of incinerators. Therefore, a method for decomposing iodofluorocarbons that consumes less energy and is economical is desired.

[0003] Also, a method has been reported in which ethylene is added to iodofluorocarbons, followed by reaction with an alkali metal hydroxide or alkali metal alkoxide in the presence of an alcohol to form an olefin, followed by heat treatment to recover a fluorine source as hydrogen fluoride, and then decomposing the iodofluorocarbons (e.g., Patent Document 1, etc.). This method has the advantage that the fluorine source can be recovered and reused, but it requires the steps of ethylene addition, olefination, and heat treatment, and therefore has the problem of a large number of steps.

[0004] Also, a method has been reported in which iodofluorocarbons are converted to hydroperfluorocarbons by reacting them with an alkali metal hydroxide in an alcohol solvent (for example, Patent Document 2). In this method, the iodine moiety can be decomposed, but the perfluoroalkane moiety remains undecomposed. In recent years, there has been a strengthening of the movement towards restricting perfluoroalkyl compounds, and a method for decomposing not only the iodine moiety but also the perfluoroalkane moiety is desired.

[0005] In addition, a method of converting iodofluorocarbons to perfluoroalkyl carboxylic acids by reacting them with a Rongalit-sodium bicarbonate reagent (e.g., Non-Patent Document 1), and a method of decomposing perfluoroalkyl carboxylic acids in the presence of a base in a dimethyl sulfoxide solvent (e.g., Non-Patent Document 2) have been reported. By using these two methods, it is possible to convert iodofluorocarbons to perfluoroalkyl carboxylic acids, and then decompose the perfluoroalkyl carboxylic acids in the presence of a base in a dimethyl sulfoxide solvent, but there is a problem in that the number of steps is large. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6021720. [Patent Document 2] Patent No. 2559312. [Non-patent literature]

[0007] [Non-Patent Document 1] Bing-Nan Huang et al., J. Fluorine Chem., 1987, 36, 49-62. [Non-Patent Document 2] Brittany Trang et al., Science, 2022, 377, 839-845. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a practical method for decomposing iodofluorocarbons into fluoroacetic acids and / or inorganic fluorides under mild conditions, i.e., an economical, safe and industrially applicable decomposition method. [Means for solving the problem]

[0009] The present inventors conducted extensive research into methods for decomposing iodofluorocarbons and as a result discovered a method for decomposing iodofluorocarbons into fluoroacetic acids and / or inorganic fluorides under mild conditions by reacting iodofluorocarbons in the presence of a solvent and a base, thereby completing the present invention.

[0010] That is, the present invention relates to the following inventions. [1] The following general formula (1) R f -I (1) (In general formula (1), R f represents a linear or branched fluoroalkyl group having 2 to 20 carbon atoms which may contain one or more iodine atoms) A method for decomposing iodofluorocarbons, comprising reacting one or more of iodofluorocarbons represented by the following formula (1): [2] The method for decomposing iodofluorocarbons according to item [1], wherein the base is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide and potassium ethoxide, and the method is characterized in that 1.0 molar equivalent to 100 molar equivalents of the base are reacted with respect to the total molar amount of fluorine atoms contained in one or more of the iodofluorocarbons represented by formula (1). [3] The method for decomposing iodofluorocarbons according to item [1], characterized in that the solvent is at least one organic solvent selected from the group consisting of dimethyl sulfoxide, sulfolane, N,N-dimethylacetamide, and N,N-dimethylformamide, or a mixed solvent consisting of such an organic solvent and water. [4] The method for decomposing iodofluorocarbons according to item [3], wherein a mixing ratio of water to the organic solvent is within a range of 100 / 0 to 10 / 90 by mass ratio. [5] The method for decomposing iodofluorocarbons according to any one of [1] to [4] above, wherein the reaction temperature is 10°C to 150°C. Effect of the Invention

[0011] The present invention provides a method capable of decomposing iodofluorocarbons into fluoroacetic acids and / or inorganic fluorides under mild conditions. [Brief description of the drawings]

[0012] [Figure 1] This shows the time course of 19F-NMR spectra during the decomposition of iodofluorocarbons in Example 9. The four spectra in the figure show the time course from top to bottom, starting at 25°C (indicated as "0h"), 1h at 25°C, 4h at 25°C, and 24h at 25°C, with the horizontal axis showing the chemical shift (ppm) of the 19F-NMR spectrum and the vertical axis being arbitrary. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in detail below. Specific examples of iodofluorocarbons represented by the general formula (1) applicable to the present invention include 1-iodopentafluoroethane, 1-iodoheptafluoropropane, 1-iodononafluorobutane, 1-iodoundecafluoropentane, 1-iodotridecafluorohexane, 1-iodopentadecafluoroheptane, 1-iodoheptadecafluorooctane, 1-iodonadecafluorononane, 1-iodohexafluorodecane, 1-iodotridecafluorohexane, 1-iodopentadecafluoroheptane, 1-iodoheptadecafluorooctane, 1-iodonadecafluorononane, 1-iodohexafluorodecane, 1-iodotridecafluorohexane ... Licosafluoroundecane, 1-iodopentacosafluorododecane, 1-iodoheptacosafluorotridecane, 1-iodonocosafluorotetradecane, 1-iodohentriacontafluoropentadecane, 1-iodoheptacosafluorohexadecane, 1-iodopentatriacontafluoroheptadecane, 1-iodoheptatriacontafluorooctadecane, 1-iodonatoriacontafluorononadecane, 1-iodoheptatriacontafluorooctadecane Iocosane, 1,2-diiodotetrafluoroethane, 1,3-diiodohexafluoropropane, 1,4-diiodooctafluorobutane, 1,5-diiododecafluoropentane, 1,6-diiodododecafluorohexane, 1,7-diiodotetradecafluoroheptane, 1,8-diiodohexadecafluorooctane, 1,9-diiodooctadecafluorononane, 1,10-diiodoicosaflodecane, 1,11-diiododocosafluoroundecane, 1,12-diiodotetracosafluorododecane, 1,13-diiodohexacosafluorotridecane, 1,14-diiodooctacosafluorotetradecane, 1,15-diiodotriacontafluoropentadecane, 1,16-diiodotriacontafluorohexadecane, 1,17-diiodotetratriacotafluoroheptadecane, 1,18-diiodohexatriacotafluorooctadecane, 1,19-diiodooctatriacotafluorononadecane, 1,20-Diiodotetrafluoroicosane, 2-iodoheptafluoropropane, 1-iodoperfluoro(2-methylpropane), 1-iodoperfluoro(3-methylbutane), 1-iodoperfluoro(4-methylpentane), 1-iodoperfluoro(5-methylhexane), 1-iodoperfluoro(6-methylheptane), 1-iodoperfluoro(7-methyloctane), 1-iodoperfluoro(8-methylnonane), 1-iodoperfluoro(9-methyldecane), cane), 1-iodoperfluoro(10-methylundecane), 1-iodoperfluoro(11-methyldodecane), 1-iodoperfluoro(12-methyltridecane), 1-iodoperfluoro(13-methyltetradecane), 1-iodoperfluoro(14-methylpentadecane), 1-iodoperfluoro(15-methylhexadecane), 1-iodoperfluoro(16-methylheptadecane), 1-iodoperfluoro(17-methyloctadecane), etc.

[0014] As the base applicable to the present invention, sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, etc. can be used, and among these, sodium hydroxide and potassium hydroxide are preferably used. These bases may be used alone, but multiple bases can also be used in combination.

[0015] The amount of base used may be 1.0 molar equivalent to 100 molar equivalents of the base relative to the total molar amount of fluorine atoms contained in one or more molecules of iodofluorocarbons represented by formula (1). That is, the total molar amount of fluorine atoms contained in one or more molecules of iodofluorocarbons used in the reaction may be calculated by fluorine analysis of the target sample to determine the amount of base used. The method for measuring the total molar amount of fluorine atoms contained in one or more molecules of iodofluorocarbons may be, for example, a method using an internal standard substance. 19 F-NMR analysis is an example.

[0016] As a solvent applicable to the present invention, at least one compound selected from the group consisting of dimethyl sulfoxide, sulfolane, N,N-dimethylacetamide, and N,N-dimethylformamide can be used. If necessary, a mixed solvent consisting of the above organic solvent and water can be used. The amount of the compound used is preferably 2 to 200 times by weight relative to the weight of the iodofluorocarbons used in the reaction. The mixing ratio of water to the organic solvent applicable to the present invention is in the range of 100 / 0 to 10 / 90 by mass ratio.

[0017] The reaction temperature applicable to the present invention varies depending on the type of iodofluorocarbon used in the reaction and the type of solvent used, but is usually within the range of 10°C to 150°C. EXAMPLES

[0018] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0019] The following instruments were used for the analysis: 19 F-NMR (282 MHz): Varian Mercury 300 and Bruker Avance 500. Ion chromatography device: Tosoh ion chromatograph IC-8100ST.

[0020] Example 1 <Decomposition of 1-iodoheptadecafluorooctane> [ka]

[0021] 1-Iodoheptadecafluorooctane (109 mg, 0.20 mmol) and sodium hydroxide (240 mg, 6.0 mmol, 30 equiv) were added to a PTFE reaction vessel. Dimethyl sulfoxide (2.0 mL) and distilled water (0.25 mL) were then added, and a PTFE cap was attached. The mixture was sonicated for approximately 30 seconds to dissolve as much as possible, and then stirred at 80°C for 24 hours. After stirring at room temperature for 30 minutes, 0.05 mL of the reaction solution was taken into a glass NMR tube using a syringe (barrel: polypropylene), and dimethyl sulfoxide-d 6 Add 0.6 mL of 19 F-NMR showed that the peak of 1-iodoheptadecafluorooctane had disappeared. The solution in the NMR tube was returned to the reaction vessel, and distilled water was added to completely dissolve the precipitate. Extraction was performed three times using diethyl ether. After diethyl ether was removed from the combined organic phase, dimethyl sulfoxide-d 6 Using 19 F-NMR was measured. After freeze-drying the aqueous layer, a part of the precipitated solid was transferred to a sample tube and the fluoride ion was quantified using an ion chromatography device (Ion Chromatograph IC-8100ST). The remaining precipitated solid from the aqueous layer was then quantified using D 2 Dissolve completely in O 19 F-NMR measurements revealed a fluorine anion peak (-119.2 ppm, s) and a sodium trifluoroacetate peak (-72.1 ppm, s).

[0022] <Ion chromatography measurement method> The aqueous layer of the reaction solution in Example 1 was freeze-dried to obtain a solid, and 5.0 mg of the solid was weighed out and placed in a 50 mL polypropylene measuring flask, and distilled water was added to obtain 50 mL of sample solution. 500 μL of the sample solution was collected using a pipette (GILSON L P1000L) and added to a 10 mL polypropylene measuring flask to prepare 10 mL of 20-fold diluted sample solution. 1.0 mL of the 20-fold diluted sample solution was taken using a syringe (barrel: polypropylene), and fluoride ion was quantified using an ion chromatography device (ion chromatograph IC-8100ST). The measurement was performed using a column (TSKgel (registered trademark) SuperIC-Anion HS), an eluent (TSKgel (registered trademark) eluent Conc. IC-A HS-10 (75 mmol / L, NaHCO 3 +8.0mmol / L Na 2 CO 3 ) was diluted 10-fold with distilled water), and an anion suppressor gel (TSKgel (registered trademark) suppress IC-A) was used, and the measurement was performed using an automatic exchange type gel suppressor method, an oven temperature of 40°C, a flow rate of 1.5 mL / min, and a loop volume of 30 μL. The retention time of fluorine anion was approximately 1.75 min, and the amount of fluorine anion was quantified from the calibration curve, resulting in a fluorine recovery rate of 77%.

[0023] Examples 2 to 12 <Decomposition of various iodofluorocarbons> Using the same reaction apparatus as in Example 1, and using an iodofluorocarbon shown in Table 1 instead of 1-iodoheptadecafluorooctane, the reaction was carried out for 24 hours at the reaction temperature shown in Table 1. After post-treatment of the reaction solution, the aqueous layer was freeze-dried to obtain a solid, and the fluoride ion content of the solid was quantitatively measured by ion chromatography. The fluorine recovery rate was calculated and the results are shown in Table 1. In addition, in Example 9 19 The change over time in the F-NMR spectrum is shown in Figure 1. As shown in Figure 1, it can be seen that iodofluorocarbons decompose into fluoroacetic acids.

[0024] [Table 1]

[0025] Examples 13 to 18 <Decomposition of various iodofluorocarbons> Using the same reaction apparatus as in Example 1, the reaction was carried out for 24 hours at the reaction temperature shown in Table 2, using the iodofluorocarbons shown in Table 2 instead of 1-iodoheptadecafluorooctane. After post-treatment of the reaction solution, the aqueous layer was freeze-dried to obtain a solid, which was subjected to quantitative measurement of fluoride ions by ion chromatography, and the fluorine recovery rate was calculated. The results are shown in Table 2. The remaining solid precipitated from the aqueous layer was then subjected to D 2 Dissolve completely in O 19 F-NMR was measured, and the fluorine recovery rate derived from sodium trifluoroacetate was calculated from the integral values ​​of the fluorine anion peak (-119.2 ppm, s) and the sodium trifluoroacetate peak (-72.1 ppm, s). The results are shown in Table 2.

[0026] [Table 2]

[0027] Examples 19 to 26 <Decomposition of various iodofluorocarbons> The same reaction apparatus as in Example 1 was used, but instead of 1-iodoheptadecafluorooctane, the iodofluorocarbons shown in Table 2 were used, and the reaction temperature and reaction time were changed to those shown in Table 3. After post-treatment of the reaction solution, the aqueous layer was freeze-dried to obtain a solid, which was subjected to quantitative measurement of fluoride ions by ion chromatography, and the fluorine recovery rate was calculated. The results are shown in Table 3. The remaining solid precipitated from the aqueous layer was then subjected to freeze-drying. 2 Dissolve completely in O 19 F-NMR was measured, and the fluorine recovery rate derived from sodium trifluoroacetate was calculated from the integral values ​​of the fluorine anion peak (-119.2 ppm, s) and the sodium trifluoroacetate peak (-72.1 ppm, s). The results are shown in Table 3.

[0028] [Table 3]

[0029] From the above Examples 22 and 26, it is understood that sodium trifluoroacetate generated by the decomposition of iodofluorocarbons can be decomposed to below the detection limit.

[0030] Example 27 <Decomposition of 1,4-diiodooctafluorobutane distillation residue> After separating 1,4-diiodooctafluorobutane by distillation from a mixture containing 1,4-diiodooctafluorobutane as the main component obtained by telomerization using tetrafluoroethylene and iodine, the high boiling point substances remaining as bottom residue were 19 F-NMR analysis revealed the composition shown in Table 4 below.

[0031] [Table 4]

[0032] Sodium hydroxide (3.58 g, 89.5 mmol), dimethyl sulfoxide (26.6 mL), and water (3.6 mL) were charged into a 100 mL eggplant-shaped flask equipped with a magnetic stirrer and stirred at room temperature for 30 minutes. Then, 1,4-diiodooctafluorobutane distillation residue (1.18 g, total molar amount of fluorine atoms is 24.18 mmol) was added to the flask and the mixture was heated in an oil bath at 60°C for 7 days. After the reaction, the mixture was cooled to room temperature and diluted with 200 mL of water to obtain a homogeneous solution. The solution was then analyzed using 2,2,2-trifluoroethanol as an internal standard. 19 Quantitative analysis by F-NMR revealed that the product had decomposed into sodium fluoride (19.82 mmol, recovery rate 82.0%) and trifluoroacetic acid (0.60 mmol, recovery rate 2.5%) based on the diiodooperfluoroalkane mixture. [Industrial Applicability]

[0033] The present invention can provide an economical, safe and industrially applicable decomposition method for decomposing iodofluorocarbons into fluoroacetic acids and / or inorganic fluorides under mild conditions.

Claims

1. The following general formula (1) R ｆ -I (1) (In general formula (1), R ｆ represents a linear or branched fluoroalkyl group having 2 to 20 carbon atoms which may contain one or more iodine atoms. A method for decomposing iodofluorocarbons, comprising reacting one or more of iodofluorocarbons represented by the following formula (1):

2. The method for decomposing iodofluorocarbons according to claim 1, characterized in that the base is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide and potassium ethoxide, and the base is reacted with 1.0 molar equivalent to 100 molar equivalents relative to the total molar amount of fluorine atoms contained in one or more of the iodofluorocarbons represented by formula (1).

3. The method for decomposing iodofluorocarbons according to claim 1, characterized in that the solvent is at least one organic solvent selected from the group consisting of dimethyl sulfoxide, sulfolane, N,N-dimethylacetamide, and N,N-dimethylformamide, or a mixed solvent consisting of any of these organic solvents and water.

4. 4. The method for decomposing iodofluorocarbons according to claim 3, wherein the mixing ratio of water to the organic solvent is in the range of 100 / 0 to 10 / 90 by mass ratio.

5. The method for decomposing iodofluorocarbons according to any one of claims 1 to 4, characterized in that the reaction temperature is 10°C to 150°C.

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